In a multi-link suspension, the wheels are attached to a central sub-frame of a vehicle by means of a plurality of arms linking or attaching the wheel stub axle with said sub-frame. Such suspensions are the object of recent technological developments made in the automotive industry. The main advantage of such suspensions is the high lateral stiffness they confer to the vehicle, thereby preventing the phenomenon known as oversteering. They also provide better directional stability in the direction of travel and allow absorbing a high percentage of vibrations and noises. In summary, with respect to suspensions of another type, multi-link suspensions provide the vehicle with greater maneuverability, safety and superior travel comfort.
The elements comprised in such suspensions include, among others, suspension arms, which are kinematic elements the function of which is to statically and dynamically define the relative position of the wheel with respect to the vehicle frame while at the same transmitting part of the stresses of the wheel to the body, and vice versa.
Today, there is a wide range of suspension arms which are obtained by means of different processes, among which stamping a sheet, forging or smelting pieces of aluminum or steel and welding bushings to tubes can be mentioned. All cases require achieving sufficient stiffness regardless of the operating or working temperature of the vehicle suspension.
A series of documents representing the most relevant and recent state of the art in reference to suspension arms is mentioned below.
Patent document JPS58188712 describes a coupling rod formed by two identical parts that are attached by means of welding applied on their flanges, said flanges being perpendicular to the longitudinal axes of the bearings. The two identical parts are shaped according to a multi-step sheet stamping and die-cutting process, said parts being symmetrical with respect to their longitudinal axis in addition to being identical. Both parts are then placed facing one another, rotating one of them 180° with respect to its longitudinal axis, and they are attached by means of spot welding on their flanges, although use of weld beads is also contemplated. Finally, the elastic bearings are introduced in the cylindrical portions and set in place. Although the fact of having identical parts reduces production costs, the facing arrangement of these parts, which also determines the configuration of their attachment shape, is far from being mechanically efficient considering the stiffness and weight of the rod.
In this same sense, patent document U.S. Pat. No. 3,121,348 describes a coupling rod formed by two identical parts that are attached by means of a weld bead applied on their flanges, unlike the case mentioned in the preceding paragraph, said flanges being parallel to the longitudinal axes of the elastic bearings. Like in the preceding case, the two identical parts are shaped according to a sheet stamping and die-cutting process, said parts being identical and symmetrical with respect to their longitudinal axis. To attach them, the parts are placed facing one another, rotating one of them 180° with respect to its longitudinal axis, and they are attached by means of a weld bead applied on their flanges. Finally, the elastic bearings are introduced in the cylindrical openings and set in place. Similarly, this arm has the limitations indicated for the preceding case.
On the other hand, patent document ES2285410T describes a suspension control arm comprising two U-shaped stamped metal parts that are attached to one another by their flanges by means of weld beads, where the flanges are parallel to the longitudinal axes of the elastic bearings. From the mechanical efficiency viewpoint, this arm is better than the two preceding arms as the attachment is formed with a overlap between said flanges; however, unlike the two preceding cases, in order to achieve said arrangement it is necessary to start from two parts that are not only asymmetrical but which are also different from one another, which increases production costs.
Therefore, in view of the foregoing a solution that is a compromise among production costs of the suspension arms for automotive vehicle multi-link suspensions, their weight and their mechanical characteristics is susceptible to improvement.